1. Field of the Invention
The present invention relates to a position changing apparatus, such as a shift range changing apparatus for vehicle automatic transmissions which changes the shift ranges by actuators such as electric motors.
2. Related Art
It is known (e.g., JP-A-5-44511) to use a direct current electric motor as a drive source for changing gear shift ranges in a vehicle automatic transmission in response to a vehicle driver's operation of a gear shift lever. If the electric motor or a drive circuit fails, however, changing the shift ranges is disabled.
U.S. Pat. No. 5,094,115 (JP-A-3-255252) proposes to use two pairs of a direct current motor and a drive circuit. One pair is used normally, and the other pair is used upon failure of the one pair so that the shift range changing operation may be enabled by either one of the pairs. However, the two pairs will result in the increase in the number of component parts and in the apparatus cost.